60 research outputs found
L-band (3.5 micron) IR-excess in massive star formation, II. RCW 57/NGC 3576
We present a JHKL survey of the massive star forming region RCW 57 (NGC 3576)
based on L-band data at 3.5 micron taken with SPIREX (South Pole Infrared
Explorer), and 2MASS JHK data at 1.25-2.2 micron. This is the second of two
papers, the first one concerning a similar JHKL survey of 30 Doradus.
Colour-colour and colour-magnitude diagrams are used to detect sources with
infrared excess. This excess emission is interpreted as coming from
circumstellar disks, and hence gives the cluster disk fraction (CDF). Based on
the CDF and the age of RCW 57, it is possible to draw conclusions on the
formation and early evolution of massive stars. The infrared excess is detected
by comparing the locations of sources in JHKL colour-colour and L vs. (K-L)
colour-magnitude diagrams to the reddening band due to interstellar extinction.
A total of 251 sources were detected. More than 50% of the 209 sources included
in the diagrams have an infrared excess. Comparison with other JHKL surveys,
including the results on 30 Doradus from the first paper, support a very high
initial disk fraction (>80%) even for massive stars, although there is an
indication of a possible faster evolution of circumstellar disks around high
mass stars. 33 sources only found in the L-band indicate the presence of
heavily embedded, massive Class I protostars. We also report the detection of
diffuse PAHs emission throughout the RCW 57 region.Comment: 15 pages, 13 figure
Photodissociation regions and star formation in the Carina Nebula
We have obtained wide-field thermal infrared (IR) images of the Carina
Nebula, using the SPIREX/Abu telescope at the South Pole. Emission from
poly-cyclic aromatic hydrocarbons (PAHs) at 3.29um, a tracer of
photodissociation regions (PDRs), reveals many interesting well defined clumps
and diffuse regions throughout the complex. Near-IR images (1--2um), along with
images from the Midcourse Space Experiment (MSX) satellite (8--21um) were
incorporated to study the interactions between the young stars and the
surrounding molecular cloud in more detail. Two new PAH emission clumps have
been identified in the Keyhole Nebula and were mapped in 12CO(2--1) and (1--0)
using the SEST. Analysis of their physical properties reveals they are dense
molecular clumps, externally heated with PDRs on their surfaces and supported
by external pressure in a similar manner to the other clumps in the region. A
previously identified externally heated globule containing IRAS 10430-5931 in
the southern molecular cloud, shows strong 3.29-, 8- and 21-um emission, the
spectral energy distribution (SED) revealing the location of an ultra-compact
(UC) HII region. The northern part of the nebula is complicated, with PAH
emission inter-mixed with mid-IR dust continuum emission. Several point sources
are located here and through a two-component black-body fit to their SEDs, we
have identified 3 possible UC HII regions as well as a young star surrounded by
a circumstellar disc. This implies that star formation in this region is
on-going and not halted by the intense radiation from the surrounding young
massive stars.Comment: 14 pages, 12 figures. Accepted by MNRAS. Higher resolution figures
available at http://www.phys.unsw.edu.au/~jmr/papers.htm
What is missing in autonomous discovery: Open challenges for the community
Self-driving labs (SDLs) leverage combinations of artificial intelligence,
automation, and advanced computing to accelerate scientific discovery. The
promise of this field has given rise to a rich community of passionate
scientists, engineers, and social scientists, as evidenced by the development
of the Acceleration Consortium and recent Accelerate Conference. Despite its
strengths, this rapidly developing field presents numerous opportunities for
growth, challenges to overcome, and potential risks of which to remain aware.
This community perspective builds on a discourse instantiated during the first
Accelerate Conference, and looks to the future of self-driving labs with a
tempered optimism. Incorporating input from academia, government, and industry,
we briefly describe the current status of self-driving labs, then turn our
attention to barriers, opportunities, and a vision for what is possible. Our
field is delivering solutions in technology and infrastructure, artificial
intelligence and knowledge generation, and education and workforce development.
In the spirit of community, we intend for this work to foster discussion and
drive best practices as our field grows
Science Programs for a 2 m-class Telescope at Dome C, Antarctica: PILOT, the Pathfinder for an International Large Optical Telescope
The cold, dry and stable air above the summits of the Antarctic plateau
provides the best ground-based observing conditions from optical to sub-mm
wavelengths to be found on the Earth. PILOT is a proposed 2 m telescope, to be
built at Dome C in Antarctica, able to exploit these conditions for conducting
astronomy at optical and infrared wavelengths. While PILOT is intended as a
pathfinder towards the construction of future grand-design facilities, it will
also be able to undertake a range of fundamental science investigations in its
own right. This paper provides the performance specifications for PILOT,
including its instrumentation. It then describes the kinds of science projects
that it could best conduct. These range from planetary science to the search
for other solar systems, from star formation within the Galaxy to the star
formation history of the Universe, and from gravitational lensing caused by
exo-planets to that produced by the cosmic web of dark matter. PILOT would be
particularly powerful for wide-field imaging at infrared wavelengths, achieving
near-diffraction limited performance with simple tip-tilt wavefront correction.
PILOT would also be capable of near-diffraction limited performance in the
optical wavebands, as well be able to open new wavebands for regular ground
based observation; in the mid-IR from 17 to 40 microns and in the sub-mm at 200
microns.Comment: 74 pages, 14 figures, PASA, in pres
Diacylglycerol-Stimulated Endocytosis of Transferrin in Trypanosomatids Is Dependent on Tyrosine Kinase Activity
Small molecule regulation of cell function is an understudied area of trypanosomatid biology. In Trypanosoma brucei diacylglycerol (DAG) stimulates endocytosis of transferrin (Tf). However, it is not known whether other trypanosomatidae respond similarly to the lipid. Further, the biochemical pathways involved in DAG signaling to the endocytic system in T. brucei are unknown, as the parasite genome does not encode canonical DAG receptors (e.g. C1-domains). We established that DAG stimulates endocytosis of Tf in Leishmania major, and we evaluated possible effector enzymes in the pathway with multiple approaches. First, a heterologously expressed glycosylphosphatidylinositol phospholipase C (GPI-PLC) activated endocytosis of Tf 300% in L. major. Second, exogenous phorbol ester and DAGs promoted Tf endocytosis in L. major. In search of possible effectors of DAG signaling, we discovered a novel C1-like domain (i.e. C1_5) in trypanosomatids, and we identified protein Tyr kinases (PTKs) linked with C1_5 domains in T. brucei, T. cruzi, and L. major. Consequently, we hypothesized that trypanosome PTKs might be effector enzymes for DAG signaling. General uptake of Tf was reduced by inhibitors of either Ser/Thr or Tyr kinases. However, DAG-stimulated endocytosis of Tf was blocked only by an inhibitor of PTKs, in both T. brucei and L. major. We conclude that (i) DAG activates Tf endocytosis in L. major, and that (ii) PTKs are effectors of DAG-stimulated endocytosis of Tf in trypanosomatids. DAG-stimulated endocytosis of Tf may be a T. brucei adaptation to compete effectively with host cells for vertebrate Tf in blood, since DAG does not enhance endocytosis of Tf in human cells
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