2,451 research outputs found
Biogeography of Wood-Boring Crustaceans (Isopoda: Limnoriidae) Established in European Coastal Waters
Marine wood-borers of the Limnoriidae cause great destruction to wooden structures exposed in the marine environment. In this study we collated occurrence data obtained from field surveys, spanning over a period of 10 years, and from an extensive literature review. We aimed to determine which wood-boring limnoriid species are established in European coastal waters; to map their past and recent distribution in Europe in order to infer species range extension or contraction; to determine species environmental requirements using climatic envelopes. Of the six species of wood-boring Limnoria previously reported occurring in Europe, only Limnoria lignorum, L. quadripunctata and L. tripunctata are established in European coastal waters. L. carinata and L. tuberculata have uncertain established status, whereas L. borealis is not established in European waters. The species with the widest distribution in Europe is Limnoria lignorum, which is also the most tolerant species to a range of salinities. L. quadripunctata and L. tripunctata appear to be stenohaline. However, the present study shows that both L. quadripunctata and L. tripunctata are more widespread in Europe than previous reports suggested. Both species have been found occurring in Europe since they were described, and their increased distribution is probably the results of a range expansion. On the other hand L. lignorum appears to be retreating poleward with ocean warming. In certain areas (e.g. southern England, and southern Portugal), limnoriids appear to be very abundant and their activity is rivalling that of teredinids. Therefore, it is important to monitor the distribution and destructive activity of these organisms in Europe
Discovery of Two New Class II Methanol Maser Transitions in G345.01+1.79
We have used the Swedish ESO Submillimetre Telescope (SEST) to search for new
class II methanol maser transitions towards the southern source G345.01+1.79.
Over a period of 5 days we observed 11 known or predicted class II methanol
maser transitions. Emission with the narrow line width and characteristic
velocity of class II methanol masers (in this source) was detected in 8 of
these transitions, two of which have not previously been reported as masers.
The new class II methanol maser transitions are the 13(-3)-12(-4)E transition
at 104.1 GHz and the 5(1)-4(2)E transition at 216.9 GHz. Both of these are from
transition series for which there are no previous known class II methanol maser
transitions. This takes the total number of known class II methanol maser
series to 10, and the total number of transitions (or transition groups) to 18.
The observed 104.1 GHz maser suggests the presence of two or more regions of
masing gas with similar line of sight velocities, but quite different physical
conditions. Although these newly discovered transitions are likely to be
relatively rare, where they are observed combined studies using the Australia
Telescope Compact Array and the Atacama Large Millimeter Array offer the
prospect to be able to undertake multi-transition methanol maser studies with
unprecedented detail.Comment: 8 pages, 3 figures, accepted for publication in ApJ Letter
A Complex Chemical Potential: Signature of Decay in a Bose-Einstein Condensate
We explore the zero-temperature statics of an atomic Bose-Einstein condensate
in which a Feshbach resonance creates a coupling to a second condensate
component of quasi-bound molecules. Using a variational procedure to find the
equation of state, the appearance of this binding is manifest in a collapsing
ground state, where only the molecular condensate is present up to some
critical density. Further, an excited state is seen to reproduce the usual
low-density atomic condensate behavior in this system, but the molecular
component is found to produce an underlying decay, quantified by the imaginary
part of the chemical potential. Most importantly, the unique decay rate
dependencies on density () and on scattering length () can be measured in experimental tests of this theory.Comment: 4 pages, 1 figur
A search for 85.5- and 86.6-GHz methanol maser emission
We have used the Australia Telescope National Facility Mopra 22m millimetre
telescope to search for emission from the 85.5-GHz and 86.6-GHz transitions of
methanol. The search was targeted towards 22 star formation regions which
exhibit maser emission in the 107.0-GHz methanol transition, as well as in the
6.6-GHz transition characteristic of class II methanol maser sources. A total
of 22 regions were searched at 85.5 GHz resulting in 5 detections, of which 1
appears to be a newly discovered maser. For the 86.6-GHz transition
observations were made of 18 regions which yielded 2 detections, but no new
maser sources. This search demonstrates that emission from the 85.5- and
86.6-GHz transitions is rare. Detection of maser emission from either of these
transitions therefore indicates the presence of special conditions, different
from those in the majority of methanol maser sources. We have observed temporal
variability in the 86.6-GHz emission towards 345.010+1.792, which along with
the very narrow line width, confirms that the emission is a maser in this
source. We have combined our current observations with published data for the
6.6-, 12.1-, 85.5-, 86.6-, 107.0-, 108.8- and 156.6-GHz transitions for
comparison with the maser model of Sobolev & Deguchi (1994). This has allowed
us to estimate the likely ranges of dust temperature, gas density, and methanol
column density, both for typical methanol maser sources and for those sources
which also show 107.0-GHz emission.Comment: 11 pages, accepted for publication in MNRAS, Latex, mn2e.cl
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
Detection of 6.7 GHz methanol absorption towards hot corinos
Methanol masers at 6.7 GHz have been found exclusively towards high-mass star
forming regions. Recently, some Class 0 protostars have been found to display
conditions similar to what are found in hot cores that are associated with
massive star formation. These hot corino sources have densities, gas
temperatures, and methanol abundances that are adequate for exciting strong 6.7
GHz maser emission. This raises the question of whether 6.7 GHz methanol masers
can be found in both hot corinos and massive star forming regions, and if not,
whether thermal methanol emission can be detected. We searched for the 6.7 GHz
methanol line towards five hot corino sources in the Perseus region using the
Arecibo radio telescope. To constrain the excitation conditions of methanol, we
observed thermal submillimeter lines of methanol in the NGC1333-IRAS 4 region
with the APEX telescope. We did not detect 6.7 GHz emission in any of the
sources, but found absorption against the cosmic microwave background in
NGC1333-IRAS 4A and NGC1333-IRAS 4B. Using a large velocity gradient analysis,
we modeled the excitation of methanol over a wide range of physical parameters,
and verify that the 6.7 GHz line is indeed strongly anti-inverted for densities
lower than 10^6 cm^-3. We used the submillimeter observations of methanol to
verify the predictions of our model for IRAS 4A by comparison with other CH3OH
transitions. Our results indicate that the methanol observations from the APEX
and Arecibo telescopes are consistent with dense (n ~ 10^6 cm^-3), cold (T ~
15-30 K) gas. The lack of maser emission in hot corinos and low-mass
protostellar objects in general may be due to densities that are much higher
than the quenching density in the region where the radiation field is conducive
to maser pumping.Comment: Accepted by A&
Delivering co-stimulatory tumor necrosis factor receptor agonism for cancer immunotherapy: past, current and future perspectives
The tumor necrosis factor superfamily (TNFSF) and their receptors (TNFRSF) are important regulators of the immune system, mediating proliferation, survival, differentiation, and function of immune cells. As a result, their targeting for immunotherapy is attractive, although to date, under-exploited. In this review we discuss the importance of co-stimulatory members of the TNFRSF in optimal immune response generation, the rationale behind targeting these receptors for immunotherapy, the success of targeting them in pre-clinical studies and the challenges in translating this success into the clinic. The efficacy and limitations of the currently available agents are discussed alongside the development of next generation immunostimulatory agents designed to overcome current issues, and capitalize on this receptor class to deliver potent, durable and safe drugs for patients
12.2-GHz methanol maser MMB follow-up catalogue - II. Longitude range 186 to 330 degrees
We present the second portion of a catalogue of 12.2-GHz methanol masers
detected towards 6.7-GHz methanol masers observed in the unbiased Methanol
Multibeam (MMB) Survey. Using the Parkes radio telescope we have targeted all
207 6.7-GHz methanol masers in the longitude range 186 to 330 degrees for
12.2-GHz counterparts. We report the detection of 83 12.2-GHz methanol masers,
and one additional source which we suspect is thermal emission, equating to a
detection rate of 40 per cent. Of the 83 maser detections, 39 are reported here
for the first time. We discuss source properties, including variability and
highlight a number of unusual sources. We present a list of 45 candidates that
are likely to harbor methanol masers in the 107.0-GHz transition.Comment: Accepted MNRAS 19 July 201
A sensitive search for predicted methanol maser transitions with the Australia telescope compact array
We have used theAustralia Telescope Compact Array to search for a number of centimetrewavelengthmethanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of 1 300 K on the brightness temperature of any emission from the 31A+-31A-, 17-2-18-3 E (vt = 1), 124-133 A-, 124-133 A+, and 41A+-41A- transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes. © Astronomical Society of Australia 2016
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