2,584 research outputs found
Multi-transition study and new detections of class II methanol masers
We have used the ATNF Mopra antenna and the SEST antenna to search in the
directions of several class II methanol maser sources for emission from six
methanol transitions in the frequency range 85-115 GHz. The transitions were
selected from excitation studies as potential maser candidates. Methanol
emission at one or more frequencies was detected from five of the maser
sources, as well as from Orion KL. Although the lines are weak, we find
evidence of maser origin for three new lines in G345.01+1.79, and possibly one
new line in G9.62+0.20.
The observations, together with published maser observations at other
frequencies, are compared with methanol maser modelling for G345.01+1.79 and
NGC6334F. We find that the majority of observations in both sources are
consistent with a warm dust (175 K) pumping model at hydrogen density ~10^6
cm^-3 and methanol column density ~5 x 10^17 cm^-2. The substantial differences
between the maser spectra in the two sources can be attributed to the geometry
of the maser region.Comment: 13 pages, 6 figures, Accepted for publication in MNRA
The Roots of Defense: Plant Resistance and Tolerance to Belowground Herbivory
There is conclusive evidence that there are fitness costs of plant defense and that herbivores can drive selection for defense. However, most work has focused on above-ground interactions, even though belowground herbivory may have greater impacts on individual plants than above-ground herbivory. Given the role of belowground plant structures in resource acquisition and storage, research on belowground herbivores has much to contribute to theories on the evolution of plant defense. Pocket gophers (Geomyidae) provide an excellent opportunity to study root herbivory. These subterranean rodents spend their entire lives belowground and specialize on consuming belowground plant parts. produced significantly more fruit than either damaged or undamaged mainland individuals.These results suggest that mainland plants are effective at deterring and tolerating pocket gopher herbivory. Results also suggest that both forms of defense are costly to fitness and thus reduced in the absence of the putative target herbivore
Integrated Diamond Optics for Single Photon Detection
Optical detection of single defect centers in the solid state is a key
element of novel quantum technologies. This includes the generation of single
photons and quantum information processing. Unfortunately the brightness of
such atomic emitters is limited. Therefore we experimentally demonstrate a
novel and simple approach that uses off-the-shelf optical elements. The key
component is a solid immersion lens made of diamond, the host material for
single color centers. We improve the excitation and detection of single
emitters by one order of magnitude, as predicted by theory.Comment: 10 pages, 3 figure
Correlation between X-ray Lightcurve Shape and Radio Arrival Time in the Vela Pulsar
We report the results of simultaneous observations of the Vela pulsar in
X-rays and radio from the RXTE satellite and the Mount Pleasant Radio
Observatory in Tasmania. We sought correlations between the Vela's X-ray
emission and radio arrival times on a pulse by pulse basis. At a confidence
level of 99.8% we have found significantly higher flux density in Vela's main
X-ray peak during radio pulses that arrived early. This excess flux shifts to
the 'trough' following the 2nd X-ray peak during radio pulses that arrive
later. Our results suggest that the mechanism producing the radio pulses is
intimately connected to the mechanism producing X-rays. Current models using
resonant absorption of radio emission in the outer magnetosphere as a cause of
the X-ray emission are explored as a possible explanation for the correlation.Comment: 6 pages, 5 figures, accepted by Ap
Fuzzy Topology, Quantization and Gauge Invariance
Dodson-Zeeman fuzzy topology considered as the possible mathematical
framework of quantum geometric formalism. In such formalism the states of
massive particle m correspond to elements of fuzzy manifold called fuzzy
points. Due to their weak (partial) ordering, m space coordinate x acquires
principal uncertainty dx. It's shown that m evolution with minimal number of
additional assumptions obeys to schroedinger and dirac formalisms in
norelativistic and relativistic cases correspondingly. It's argued that
particle's interactions on such fuzzy manifold should be gauge invariant.Comment: 12 pages, Talk given on 'Geometry and Field Theory' conference,
Porto, July 2012. To be published in Int. J. Theor. Phys. (2015
Bounds on the growth of high Sobolev norms of solutions to 2D Hartree Equations
In this paper, we consider Hartree-type equations on the two-dimensional
torus and on the plane. We prove polynomial bounds on the growth of high
Sobolev norms of solutions to these equations. The proofs of our results are
based on the adaptation to two dimensions of the techniques we previously used
to study analogous problems on , and on .Comment: 38 page
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