8,727 research outputs found
Cleaning up Eta Carinae: Detection of Ammonia in the Homunculus
We report the first detection of ammonia in the Homunculus nebula around eta
Carinae, which is also the first detection of emission from a polyatomic
molecule in this or any other luminous blue variable (LBV) nebula. Observations
of the NH3 (J,K)=(3,3) inversion transition made with the Australia Telescope
Compact Array reveal emission at locations where infrared H2 emission had been
detected previously, near the strongest dust emission in the core of the
Homunculus. We also detect ammonia emission from the so-called ``strontium
filament'' in the equatorial disk. The presence of NH3 around eta Car hints
that molecular shells around some Wolf-Rayet stars could have originated in
prior LBV eruptions, rather than in cool red supergiant winds or the ambient
interstellar medium. Combined with the lack of any CO detection, NH3 seems to
suggest that the Homunculus is nitrogen rich like the ionized ejecta around eta
Car. It also indicates that the Homunculus is a unique laboratory in which to
study unusual molecule and dust chemistry, as well as their rapid formation in
a nitrogen-rich environment around a hot star. We encourage future observations
of other transitions like NH3 (1,1) and (2,2), related molecules like N2H+, and
renewed attempts to detect CO.Comment: 4 pages, accepted to ApJ letter
Simulation analysis of energy production in the B. C. pulp and paper industry
ABSTRACT
This paper describes a dynamic simulation model of energy production
and use by pulp and paper mills. The model can be used to assess the costs
and benefits of the use of different proportions of wood waste (referred
to as 'hog fuel') and fossil fuels to generate process steam and electricity,
with the costs and benefits measured from several points of view, principally
those of the mill management and of the economy as a whole. Using either
point of view, the model has been fitted to the eighteen major pulp and paper
mills in British Columbia, and used to assess the consequences of the size and
nature of optimal hog fuel projects. Some results are reported in this
paper and references are given to other papers containing more complete
results of various aspects of the research project.
INTRODUCTION
Whenever there are big changes in technology or relative prices, many
of the standard rules of thumb for optimal choices fall apart, and many
new alternatives have to be considered in a systematic way. This offers
great scope for the design and use of simulation models that capture the
key elements of an industrial process and expose the key alternatives for
This paper was presented to the conference on Simulation Modelling
and Decision in Energy Systems, held in Montreal in June, 1978 and
sponsored by the International Association of Science and Technology
for Development. It represents early results of work also reported in
[1], [2], [3] and [4]. While Helliwell is a continuing member of U.B.C.'s
Department of Economics, Cox is currently at M.I.T.'s Energy Laboratory
Cambridge, Mass
Tracking and Testing Of US and Canadian Cattle Herds for BSE: A Risk Management Dilemma
Livestock Production/Industries,
Music Score Approval Plans in Research Libraries: A Survey of Librarian Satisfaction With and Without Approval Plans
In this study, the researchers submitted a music score approval plan survey to all ARL libraries. Two surveys were created, one for libraries with music score approval plans, one for those without. Forty-four surveys were returned. The authorsâ purpose was to analyze and discuss the survey results, incorporating elements of the scholarly work preceding this study. Discussions, roundtables, and listservs participated in by music librarians over the years formed the basis of the topic at hand. The goal was to ascertain whether these discussions and underlying assumptions of approval plans held true to the real world
Nystagmus during an acute MĂ©niĂšre's attack: From prodrome to recovery
OBJECTIVE: We are currently undertaking a clinical investigation to evaluate the diagnostic capability of a system for detecting periods of pathological dizziness. This article presents an analysis of the data captured during an acute attack of MĂ©niĂšre's disease. DESIGN: The Continuous Ambulatory Vestibular Assessment (CAVA) device is worn by patients in the community, and continuously records eye and head movement data (vestibular telemetry). STUDY SAMPLE: A 53-year-old lady with a fifteen-year history of left-sided unilateral MĂ©niĂšre's disease. RESULTS: The patient wore the device nearly continuously for thirty days. The data revealed a three-hour long attack of vertigo consisting of four separate phases of nystagmus. The duration, beat-direction and slow phase velocity of the nystagmus evolved through time. The first phase contained isolated nystagmus beats which preceded the patient's record of the vertigo attack onset but coincided with anticipation of an impending vertigo attack. CONCLUSIONS: CAVA provides a unique insight into the physiological parameters present during episodes of dizziness. Here, it has provided the first full example of an acute MĂ©niĂšre's attack, including a period of prodrome. These findings have implications for the prediction of vertigo attack onset, for the diagnosis of MĂ©niĂšre's disease and other diseases resulting in dizziness
High Resolution 8 mm and 1 cm Polarization of IRAS 4A from the VLA Nascent Disk and Multiplicity (VANDAM) Survey
Magnetic fields can regulate disk formation, accretion and jet launching.
Until recently, it has been difficult to obtain high resolution observations of
the magnetic fields of the youngest protostars in the critical region near the
protostar. The VANDAM survey is observing all known protostars in the Perseus
Molecular Cloud. Here we present the polarization data of IRAS 4A. We find that
with ~ 0.2'' (50 AU) resolution at {\lambda} = 8.1 and 10.3 mm, the inferred
magnetic field is consistent with a circular morphology, in marked contrast
with the hourglass morphology seen on larger scales. This morphology is
consistent with frozen-in field lines that were dragged in by rotating material
entering the infall region. The field morphology is reminiscent of rotating
circumstellar material near the protostar. This is the first polarization
detection of a protostar at these wavelengths. We conclude from our
observations that the dust emission is optically thin with {\beta} ~ 1.3,
suggesting that mm/cm-sized grains have grown and survived in the short
lifetime of the protostar.Comment: Accepted to ApJL. 13 pages, 4 figure
Protoplanetary Disks in Ophiuchus as Seen From ALMA
We present a high angular resolution (), high
sensitivity ( mJy) survey of the 870 m continuum emission
from the circumstellar material around 49 pre-main sequence stars in the
Ophiuchus molecular cloud. Because most millimeter instruments have resided in
the northern hemisphere, this represents the largest high-resolution,
millimeter-wave survey of the circumstellar disk content of this cloud. Our
survey of 49 systems comprises 63 stars; we detect disks associated with 29
single sources, 11 binaries, 3 triple systems and 4 transition disks. We
present flux and radius distributions for these systems; in particular, this is
the first presentation of a reasonably complete probability distribution of
disk radii at millimeter-wavelengths. We also compare the flux distribution of
these protoplanetary disks with that of the disk population of the
Taurus-Auriga molecular cloud. We find that disks in binaries are both
significantly smaller and have much less flux than their counterparts around
isolated stars. We compute truncation calculations on our binary sources and
find that these disks are too small to have been affected by tidal truncation
and posit some explanations for this. Lastly, our survey found 3 candidate
gapped disks, one of which is a newly identified transition disk with no
signature of a dip in infrared excess in extant observations.Comment: 26 pages, 16 figures. Accepted for publication in Ap
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