174 research outputs found
The first 8-13 micron spectra of globular cluster red giants: circumstellar silicate dust grains in 47 Tucanae (NGC 104)
We present 8-13 micron spectra of eight red giants in the globular cluster 47
Tucanae (NGC 104), obtained at the European Southern Observatory 3.6m
telescope. These are the first mid-infrared spectra of metal-poor, low-mass
stars. The spectrum of at least one of these, namely the extremely red,
large-amplitude variable V1, shows direct evidence of circumstellar grains made
of amorphous silicate.Comment: Accepted for publication in Astronomy and Astrophysics, 5 page
Cahiers d’études médiévales, 2 : La Science de la nature : théories et pratiques, Montréal, Bellarmin et Paris, Vrin, 1974, 199 p.
Background:
Sentinel Lymph Node (SLN) sampling may significantly reduce surgical morbidity by avoiding needless radical lymphadenectomy. In gynaecological cancers, the current practice in the UK is testing the accuracy of SLN detection using radioactive isotopes within the context of clinical trials. However, radioactive tracers pose significant logistic problems. We, therefore, conducted a pilot, observational study to assess the feasibility of a novel optical imaging device for SLN detection in gynaecological cancers using near infrared (NIR) fluorescence.
Methods:
A novel, custom-made, optical imaging system was developed to enable detection of multiple fluorescence dyes and allow simultaneous bright-field imaging during open surgery and laparoscopic procedures. We then evaluated the performance of the system in a prospective study of 49 women with early stage vulval, cervical and endometrial cancer who were scheduled to undergo complete lymphadenectomy. Clinically approved fluorescent contrast agents indocyanine green (ICG) and methylene blue (MB) were used. The main outcomes of the study included SLN mapping detection rates, false negative rates using the NIR fluorescence technique and safety of the procedures. We also examined the association between injection sites and differential lymphatic drainage in women with endometrial cancer by fluorescence imaging of ICG and MB.
Results:
A total of 64 SLNs were detected during both open surgery and laparoscopy. Following dose optimisation and the learning phase, SLN detection rate approached 100 % for all cancer types with no false negatives detected. Fluorescence from ICG and MB detected para-aortic SLNs in women with endometrial cancer following uterine injection. Percutaneous SLN detection was also achieved in most women with vulval cancer. No adverse reactions associated with the use of either dyes were observed.
Conclusions:
This study demonstrated the successful clinical application of a novel NIR fluorescence imaging system for SLN detection across different gynaecological cancers. We showcased the first in human imaging, during the same procedure, of two fluorescence dyes in women with endometrial cancer. </p
A Spitzer Study of Comets 2P/Encke, 67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT)
We present infrared images and spectra of comets 2P/Encke,
67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT) as part of a larger
program to observe comets inside of 5 AU from the sun with the Spitzer Space
Telescope. The nucleus of comet 2P/Encke was observed at two vastly different
phase angles (20 degrees and 63 degrees). Model fits to the spectral energy
distributions of the nucleus suggest comet Encke's infrared beaming parameter
derived from the near-Earth asteroid thermal model may have a phase angle
dependence. The observed emission from comet Encke's dust coma is best-modeled
using predominately amorphous carbon grains with a grain size distribution that
peaks near 0.4 microns, and the silicate contribution by mass to the sub-micron
dust coma is constrained to 31%. Comet 67P/Churyumov-Gerasimenko was observed
with distinct coma emission in excess of a model nucleus at a heliocentric
distance of 5.0 AU. The coma detection suggests that sublimation processes are
still active or grains from recent activity remain near the nucleus. Comet
C/2001 HT50 (LINEAR-NEAT) showed evidence for crystalline silicates in the
spectrum obtained at 3.2 AU and we derive a silicate-to-carbon dust ratio of
0.6. The ratio is an order of magnitude lower than that derived for comets
9P/Tempel 1 during the Deep Impact encounter and C/1995 O1 (Hale-Bopp).Comment: Accepted for publication in the Astrophysical Journal 48 pages, 15
figures, 10 table
Spitzer IRAC Observations of Star Formation in N159 in the LMC
We present observations of the giant HII region complex N159 in the LMC using
IRAC on the {\it Spitzer Space Telescope}. One of the two objects previously
identified as protostars in N159 has an SED consistent with classification as a
Class I young stellar object (YSO) and the other is probably a Class I YSO as
well, making these two stars the youngest stars known outside the Milky Way. We
identify two other sources that may also be Class I YSOs. One component,
N159AN, is completely hidden at optical wavelengths, but is very prominent in
the infrared. The integrated luminosity of the entire complex is L L, consistent with the observed radio emission assuming a
normal Galactic initial mass function (IMF). There is no evidence for a red
supergiant population indicative of an older burst of star formation. The N159
complex is 50 pc in diameter, larger in physical size than typical HII regions
in the Milky Way with comparable luminosity. We argue that all of the
individual components are related in their star formation history. The
morphology of the region is consistent with a wind blown bubble $\approx
1-2Myr-old that has initiated star formation now taking place at the rim. Other
than its large physical size, star formation in N159 appears to be
indistinguishable from star formation in the Milky Way.Comment: 14 figure
The role of citizen science in meeting SDG targets around soil health
Healthy soils are vital for sustainable development, yet consistent soil monitoring is scarce, and soils are poorly represented in United Nations Sustainable Development Goals targets and indicators. There is a clear need for specific ambitions on soil health, accompanying metrics, and cost-effective monitoring methodologies. In this paper, we review citizen science methods and platforms which could compliment structured soil monitoring programmes and contribute to filling this knowledge gap. We focussed on soil structure, organic carbon, biodiversity, nutrients, and vegetation cover. Each method was classified as red, amber, or green (RAG) in terms of time requirements, cost, and data reliability. Toolkits were assessed in terms of cost and requirement for specialist kit. We found 32 methods across the five indicators. Three soil monitoring methods scored green on all criteria, and 20 (63%) scored green on two criteria. We found 13 toolkits appropriate for citizen science monitoring of soil health. Three of them are free, easy to use, and do not require specialist equipment. Our review revealed multiple citizen science methods and toolkits for each of the five soil health indicators. This should pave the way towards a cost-effective, joined-up approach on soil health, informing national and international policy and supporting the move towards farmer-led, data-driven decision-making
Stellar Populations and Mass-Loss in M15: A Spitzer Detection of Dust in the Intra-Cluster Medium
We present Spitzer Space Telescope IRAC and MIPS observations of the galactic
globular cluster M15 (NGC 7078), one of the most metal-poor clusters with a
[Fe/H] = -2.4. Our Spitzer images reveal a population of dusty red giants near
the cluster center, a previously detected planetary nebula (PN) designated
K648, and a possible detection of the intra-cluster medium (ICM) arising from
mass loss episodes from the evolved stellar population. Our analysis suggests 9
(+/-2) x 10^-4 solar masses of dust is present in the core of M15, and this
material has accumulated over a period of approximately 10^6 years, a timescale
ten times shorter than the last galactic plane crossing event. We also present
Spitzer IRS follow up observations of K648, including the detection of the
[NeII] 12.81 micron line, and discuss abundances derived from infrared fine
structure lines.Comment: Accepted for publication in AJ. 20 pages, 10 figures, 6 tables. Full
resolution versions of figures 1, 5, 7, and 8 are available in a PDF version
of this manuscript at http://ir.astro.umn.edu/~mboyer/ms_060906.pd
A Spitzer Space Telescope Atlas of omega Centauri: The Stellar Population, Mass Loss, and the Intracluster Medium
We present a Spitzer Space Telescope imaging survey of the most massive
Galactic globular cluster, omega Centauri, and investigate stellar mass loss at
low metallicity and the intracluster medium (ICM). The survey covers
approximately 3.2x the cluster half-mass radius at 3.6, 4.5, 5.8, 8, and 24
microns, resulting in a catalog of over 40,000 point-sources in the cluster.
Approximately 140 cluster members ranging 1.5 dex in metallicity show a red
excess at 24 microns, indicative of circumstellar dust. If all of the dusty
sources are experiencing mass loss, the cumulative rate of loss is estimated at
2.9 - 4.2 x 10^(-7) solar masses per year, 63% -- 66% of which is supplied by
three asymptotic giant branch stars at the tip of the Red Giant Branch (RGB).
There is little evidence for strong mass loss lower on the RGB. If this
material had remained in the cluster center, its dust component (> 1 x 10^(-4)
solar masses) would be detectable in our 24 and 70 micron images. While no dust
cloud located at the center of omega Cen is apparent, we do see four regions of
very faint, diffuse emission beyond two half-mass radii at 24 microns. It is
unclear whether these dust clouds are foreground emission or are associated
with omega Cen. In the latter case, these clouds may be the ICM in the process
of escaping from the cluster.Comment: 20 pages, 18 figures, 8 tables, accepted for publication in A
A Spitzer search for cold dust within globular clusters
Globular cluster stars evolving off the main sequence are known to lose mass,
and it is expected that some of the lost material should remain within the
cluster as an intracluster medium (ICM). Most attempts to detect such an ICM
have been unsuccessful. The Multiband Imaging Photometer for Spitzer on the
Spitzer Space Telescope was used to observe eight Galactic globular clusters in
an attempt to detect the thermal emission from ICM dust. Most clusters do not
have significant detections at 70 microns; one cluster, NGC 6341, has tentative
evidence for the presence of dust, but 90 micron observations do not confirm
the detection. Individual 70 micron point sources which appear in several of
the cluster images are likely to be background galaxies. The inferred dust mass
and upper limits are < 4e-4 solar masses, well below expectations for cluster
dust production from mass loss in red and asymptotic giant branch stars. This
implies that either globular cluster dust production is less efficient, or that
ICM removal or dust destruction is more efficient, than previously believed. We
explore several possibilities for ICM removal and conclude that present data do
not yet permit us to distinguish between them.Comment: AJ in press; 30 pages with 8 figure
JWST NIRCam Observations of SN 1987A: Spitzer Comparison and Spectral Decomposition
JWST NIRCam observations at 1.5-4.5 m have provided broad and narrow
band imaging of the evolving remnant of SN 1987A with unparalleled sensitivity
and spatial resolution. Comparing with previous marginally spatially resolved
Spitzer IRAC observations from 2004-2019 confirms that the emission arises from
the circumstellar equatorial ring (ER), and the current brightness at 3.6 and
4.5 m was accurately predicted by extrapolation of the declining
brightness tracked by IRAC. Despite the regular light curve, the NIRCam
observations clearly reveal that much of this emission is from a newly
developing outer portion of the ER. Spots in the outer ER tend to lie at
position angles in between the well-known ER hotspots. We show that the bulk of
the emission in the field can be represented by 5 standard spectral energy
distributions (SEDs), each with a distinct origin and spatial distribution.
This spectral decomposition provides a powerful technique for distinguishing
overlapping emission from the circumstellar medium (CSM) and the supernova (SN)
ejecta, excited by the forward and reverse shocks respectively.Comment: Accepted for publication in ApJ. 16 pages, 12 figures. 2 animations
not included her
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