3,228 research outputs found
The Coldest Place in the Universe: Probing the Ultra-Cold Outflow and Dusty Disk in the Boomerang Nebula
Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is the
coldest known object in the Universe, with a massive high-speed outflow that
has cooled significantly below the cosmic background temperature. Our new CO
1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow,
out to AU. We find that in the ultra-cold outflow, the
mass-loss rate (dM/dt) increases with radius, similar to its expansion velocity
() - taking , we find . The mass in
the ultra-cold outflow is Msun, and the Boomerang's main-sequence
progenitor mass is Msun. Our high angular resolution (0".3) CO
J=3-2 map shows the inner bipolar nebula's precise, highly-collimated shape,
and a dense central waist of size (FWHM) 1740 AU AU. The
molecular gas and the dust as seen in scattered light via optical HST imaging
show a detailed correspondence. The waist shows a compact core in thermal dust
emission at 0.87-3.3 mm, which harbors Msun~of very large
(mm-to-cm sized), cold ( K) grains. The central waist
(assuming its outer regions to be expanding) and fast bipolar outflow have
expansion ages of yr and yr: the "jet-lag" (i.e.,
torus age minus the fast-outflow age) in the Boomerang supports models in which
the primary star interacts directly with a binary companion. We argue that this
interaction resulted in a common-envelope configuration while the Boomerang's
primary was an RGB or early-AGB star, with the companion finally merging into
the primary's core, and ejecting the primary's envelope that now forms the
ultra-cold outflow.Comment: accepted ApJ, 12 Apr, 201
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A study of changes in algal population density diversity and distribution and changes in physical and chemical characteristics of Lake Elsinore
High magnetic field superconducting properties of Nb3Sn films Final report
High magnetic field superconducting properties of niobium stannide films and shielding characterictics of stannide layer
ALMA view of the circumstellar environment of the post-common-envelope-evolution binary system HD101584
We study the circumstellar evolution of the binary HD101584, consisting of a
post-AGB star and a low-mass companion, which is most likely a
post-common-envelope-evolution system. We used ALMA observations of the 12CO,
13CO, and C18O J=2-1 lines and the 1.3mm continuum to determine the morphology,
kinematics, masses, and energetics of the circumstellar environment. The
circumstellar medium has a bipolar hour-glass structure, seen almost pole-on,
formed by an energetic jet, about 150 km/s. We conjecture that the
circumstellar morphology is related to an event that took place about 500 year
ago, possibly a capture event where the companion spiraled in towards the AGB
star. However, the kinetic energy of the accelerated gas exceeds the released
orbital energy, and, taking into account the expected energy transfer
efficiency of the process, the observed phenomenon does not match current
common-envelope scenarios. This suggests that another process must augment, or
even dominate, the ejection process. A significant amount of material resides
in an unresolved region, presumably in the equatorial plane of the binary
system.Comment: A&A Letter, accepte
Electromagnetic Polarizabilities and Charge Radii of the Nucleons in the Diquark-model
The diquark model is used to calculate the electromagnetic polarizabilities
and charge radii of the nucleons for three different potentials. Making the
scalar diquark lower in mass introduces a mixing angle between the
and states ,which allows an
improvement in value of all 6 properties. Generalizing the Gamov-Teller matrix
and the magnetic moment operator to the diquark model gives constraints on this
mixing. We obtain for the Richardson potential
Additional pion cloud contributions could
improve on all six results.Comment: 15 Pages, Latex, Figs on request, to be published Phys.Lett.B. Minor
errors corrected and eqn 5,6,8,9 correcte
Some Effects of 30 Years of Weir-Management on Coastal Marsh Aquatic Vegetation and Implications to Waterfowl Management
Aquatic vegetation was compared between weir-managed and unmanaged brackish marsh ponds at Marsh Island, Louisiana, parts of which have been weir-managed since 1958. Coverage by aquatic vegetation was greater in weir-managed ponds than in unmanaged ponds, but weir-management affected individual species differently. Eleocharis parvula was more common in unmanaged ponds than in managed ponds during the early 1960s but has not occurred in any ponds sampled since then. Ceratophyllum demersum and the dominant plants Myriophyllum spicatum and Ruppia maritima were more common in weir-managed ponds than in unmanaged ponds, although the magnitude of the difference varied greatly among sample dates. Because Myriophyllum spicatum and Ruppia maritima are important and preferred duck foods in Louisiana brackish marsh, it was concluded that weir-management improved habitat quality for migrant and resident ducks at Marsh Island. Weir-managed ponds contained more aquatic vegetation than unmanaged ponds in 1988, even though the crest of weirs had lost 15 cm of elevation relative to rising sea level and the accreting marsh surface. This suggests that aquatic vegetation can be increased with a greater degree of water exchange than previously believed, which is desired to reduce interference to juvenile fish and crustacean movement. Weir-managed and unmanaged ponds did not differ in pond depth, which suggests that weir-management did not affect sedimentation
The Breathing Modes of the Skyrmion and the Spin-Orbit Interaction
The coupling of the breathing and rotational modes of the skyrmion-skyrmion
system leads to a nucleon-nucleon spin-orbit interaction of short range, as
well as to spin-orbit potentials for the transitions , and . The longest range behaviour of these
spin-orbit potentials is calculated in closed form.Comment: Latex, figures not include
The middle Pleistocene transition by frequency locking and slow ramping of internal period
The increase in glacial cycle length from approximately to on average
thousand years around million years ago, called the Middle
Pleistocene Transition (MPT), lacks a conclusive explanation. We describe a
dynamical mechanism which we call Ramping with Frequency Locking (RFL), that
explains the transition by an interaction between the internal period of a
self-sustained oscillator and forcing that contains periodic components. This
mechanism naturally explains the abrupt increase in cycle length from
approximately to thousand years observed in proxy data, unlike some
previously proposed mechanisms for the MPT. A rapid increase in durations can
be produced by a rapid change in an external parameter, but this assumes rather
than explains the abruptness. In contrast, models relying on frequency locking
can produce a rapid change in durations assuming only a slow change in an
external parameter. We propose a scheme for detecting RFL in complex,
computationally expensive models, and motivate the search for climate variables
that can gradually increase the internal period of the glacial cycles.Comment: 14 pages, 12 figure
Cardiovascular changes after administration of aerosolized salbutamol in horses: five cases
Prevention and treatment of intraoperative hypoxemia in horses is difficult and both efficacy and safety of therapeutic maneuvers have to be taken into account. Inhaled salbutamol has been suggested as treatment of hypoxia in horses during general anesthesia, due to safety and ease of the technique. The present report describes the occurrence of clinically relevant unwanted cardiovascular effects (i.e. tachycardia and blood pressure modifications) in 5 horses undergoing general anesthesia in dorsal recumbency after salbutamol inhalation. Balanced anesthesia based on inhalation of isoflurane in oxygen or oxygen and air and continuous rate infusion (CRI) of lidocaine, romifidine, or combination of lidocaine and guaifenesine and ketamine was provided. Supportive measures were necessary to restore normal cardiovascular function in all horses but no long-term adverse effects were noticed in any of the cases
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